Integrated Laser Additive Manufacturing of α-AlO Nanoparticle-Seeded β/γ' Ni-Al Intermetallic Alloy with Enhanced High-Temperature Oxidation Performance.

The oxidation of β-NiAl at high temperatures leads to the preferential formation of metastable alumina, such as θ-AlO, which exhibits a significantly faster growth rate compared to stable α-AlO. However, our recent research has shown that through the use of the surface-dispersing nanoparticles (NPs) of metal oxides with a hexagonal closed pack (hcp), such as α-AlO, the thermal growth of α-AlO can be facilitated. The present study employed laser additive manufacturing (LAM) to develop an integrated α-AlO NPs surface-seeded two-phase intermetallic alloy comprising brittle β-NiAl and tougher γ'-NiAl, which demonstrated better comprehensive mechanical properties. It was found that seeding the α-AlO NPs promoted the early stage growth of α-AlO on both β and γ' phases during oxidation in air at 1000 °C. This led to a decrease in the oxidation rate but an enhancement in adhesion of the formed alumina scale in comparison to the naked β/γ' two-phase alloy. The reasons for this result were interpreted.